Allen & Heath GPIO Switching Interface: inputs, relays and wiring guide
The Allen & Heath GPIO is a small control interface that connects switches, buttons and other equipment to your Allen & Heath system over the network. It has 8 inputs, 8 relay outputs and two 10 V supply terminals on Phoenix plugs, and runs on PoE or the supplied 12 V adapter. Click any connector on the rear panel to see what it does.
- Half rack, 1U
- 8 opto inputs
- 8 relay outputs
- 2 x +10 V out
- PoE or 12 V DC
- Phoenix terminals
GPIO specifications
| Model | GPIO |
| Size | 171 x 203 x 43 mm (6.75 x 8 x 1.7 in.), W x D x H |
| Weight | 1.2 kg (2.7 lb) |
| Rack fit | 1U high, half the width of a 19 in. rack with the optional mounting accessory |
| Inputs | 8 optically isolated, switched to ground |
| Outputs | 8 relays: 7 normally open, output 1 switchable N/O or N/C |
| Relay rating | 24 V, 400 mA max, 10 W contact rating |
| Supply outputs | 2 x +10 V DC, 500 mA max combined |
| Network | RJ45, PoE (IEEE 802.3af) |
| Power | 12 V DC adapter (supplied) or PoE |
| Default IP | 192.168.1.75, subnet 255.255.255.0 |
| Status LEDs | Pwr, Lnk, Act on the front |
| Operating temperature | 0 to 35 °C (32 to 95 °F) |
Every connection on the GPIO, explained
Click a card to light up those connectors on the panel above.
8 inputs2 on the panel
The top Phoenix plug carries inputs 1 to 8, with a ground terminal at each end. An input triggers when you connect it to ground, so a plain push button, wall switch or contact closure from another system is all you need.
Use them for things like a wall panel that recalls a scene, a talk button that unmutes a paging mic, or a fire alarm contact that mutes the system. The inputs are opto-isolated, which keeps the other equipment electrically separate from the GPIO.
8 relay outputs4 on the panel
The two lower Phoenix plugs carry the relay outputs: relays 1 to 4 on the left plug and 5 to 8 on the right. Each relay is a pair of terminals that close when the output is switched on, like a remote-controlled switch.
Use them to drive on-air lights, door signs, screen controls, amplifier standby or show triggers for other systems. Relays 2 to 8 are normally open. Relay 1 can be set to normally closed with an internal option.
Each relay is rated at 24 V and 400 mA (10 W) at most. To switch anything bigger, such as mains lighting, have the GPIO drive a separate contactor or relay that is rated for the load.
+10 V supply terminals4 on the panel
The first terminal on each Out plug, marked V+, supplies +10 V DC. Together they can deliver 500 mA. Use them to power LED indicators or small loads that the relays switch, with no separate power supply.
Network port (PoE)1 on the panel
The RJ45 port connects the GPIO to your Allen & Heath system network over Cat5 or better. It accepts PoE (IEEE 802.3af), so a PoE switch can power the unit over the same cable.
DC In1 on the panel
If you don't have PoE, power the GPIO from the supplied 12 V adapter. Allen & Heath says to use only the supplied power supply (ENG Electric 6A-161WP12, A&H part AM10314).
Reset the network. The recessed switch next to DC In restores the default IP address, 192.168.1.75 with subnet 255.255.255.0. Hold it in while you power the unit up.
The front panel
- Pwr lights when the unit has power.
- Lnk confirms a physical network connection.
- Act shows network activity.
Wiring tips
- Wire inputs as a switch between the input terminal and a ground terminal. Don't put voltage on an input.
- For an LED indicator, run V+ through a relay to the LED (with a suitable resistor) and back to ground.
- Label each Phoenix plug before you unplug it. The plugs pull off, so you can wire them on the bench and plug them in at the rack.
- Keep relay loads within 24 V and 400 mA.
Mounting the GPIO
The GPIO is a small box, 171 mm (6.75 in.) wide, that can sit on a desk or shelf. With the optional mounting accessory it rack mounts at 1U high and half the rack width. The accessory takes two units side by side, or one unit with a blank in the other half. Up to 8 GPIO units can be used in one system.
Setting it up
- Connect the GPIO to the same network as your Allen & Heath system, using a PoE port or the 12 V adapter for power.
- Check that Pwr and Lnk light on the front.
- Make sure the GPIO's IP address is in the same range as the system. The default is 192.168.1.75.
- Set up what each input and output does from the mixer surface or the system's control software.
Frequently asked questions
How do I trigger an input on the Allen & Heath GPIO?+
Connect the input terminal to ground with a switch, button or dry contact. The inputs are switched to ground and are opto-isolated.
What can the GPIO relays switch?+
Up to 24 V at 400 mA (10 W) per relay. For bigger loads, use the relay to drive a separate contactor rated for the load.
Can the Allen & Heath GPIO run on PoE?+
Yes. The network port accepts PoE (IEEE 802.3af). You can also power it from the supplied 12 V DC adapter.
What is the default IP address of the GPIO?+
192.168.1.75 with subnet 255.255.255.0. Hold the recessed reset switch while powering up to go back to it.
Is the GPIO rack mountable?+
Yes, with the optional mounting accessory. It takes up 1U and half the rack width, and two units fit side by side.
Can a GPIO relay be normally closed?+
Relay 1 can be set to normally closed with an internal option. The other seven relays are normally open.
Plan this control interface in your rack
The GPIO is in the Allen & Heath library for DaMatrix, with every port mapped so you can drag it into a rack, patch it and print the documentation.
Summarized from the Allen & Heath GPIO Getting Started Guide and GPIO technical datasheet. This page is a quick reference; check the full manual for safety warnings and model-specific limits.